Earthquake Engineering

Earthquakes are one of the most devastating forces on the planet. The seismic waves that travel through the ground can demolish buildings, kill people, and cost billions of dollars in damage and restoration. According to the National Earthquake Information Center, there are over 20,000 earthquakes every year on average, including 16 major disasters. The damage was caused by the collapse of buildings with people inside, as in previous earthquakes, prompting the development of earthquake-resistant constructions.

Constructions intended to withstand earthquakes are known as earthquake-resistant structures. While no structure can be completely safe from earthquake damage, earthquake-resistant construction aims to build structures that perform better than their conventional equivalents during seismic activity. Building rules state that earthquake-resistant constructions must be able to withstand the greatest earthquake with a reasonable chance of occurring at their site. There are now various design philosophies in earthquake engineering that use experimental results, computer models, and historical earthquake observations to provide the requisite performance for the seismic threat at the location of interest. In this article, we will deal with numerous techniques that can help improve a structure.

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A large number of existing buildings do not have adequate earthquake resistant features as specified as in IS Codes. This is because of some reasons like non availability of competent technical manpower, lack of regulatory mechanisms to check earthquake resistance of proposed constructions and economic constraints.

Earthquake creates great devastations in terms of life, money and failure of structure. It is very important to upgrade certain building systems to make them more resistant to seismic activity. The structures can be earthquake damaged or earthquake vulnerable. Retrofitting proves to be a better economic consideration and immediate shelter to problems rather than replacement of the building. Retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. Retrofitting techniques are also applicable for other natural hazards such as cyclones, tornadoes and wind forces.

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Earthquake causes ground motions in a random fashion, both horizontally and vertically in all directions from the epicenter. As a result, the structures found in the ground vibrate, inducing inertial forces on them. It is therefore essential to ensure stability, strength, and serviceability with acceptable levels of safety by suitable design and detailing.

Due to horizontal shaking of the ground, horizontal inertia forces are generated at the level of the mass of the structure. The lateral inertia forces are transferred by the floor slab to the walls or columns, to the foundations, and finally to the soil. So each of the structural elements like floor slabs, walls, columns, foundations, and connections between them must be designed to safely transfer these inertia forces through them.

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INTRODUCTION
Seismic method of analysis is done in order to ascertain the various responses of buildings during earthquake and also to adopt the retrofitting of structures. It is an important tool for earthquake prone areas like Japan, North-East of India, Nepal, Philippines, and many more. This method of analysis is also important for design of elements of RCC buildings like beam, column, slab which are designed in accordance to IS 13920:2016. The seismic forces are dynamic in nature and these forces are tested for load carrying capacity, ductility, dampness, stiffness and mass. IS 1893:2016 is used to carry out seismic analysis of multi-storeyed building.
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By
Technical paper Presented by:
Mr.Jismon Issac B.E (Mech) A.I.E, MBA

Over the past few years, India has seen a spurt in the vertical growth of buildings. They range from individual houses to very tall skyscrapers. Whenever news on earthquake is reported, we have only one question in our mind – Is our home safe during an earthquake?

Engineers always tell us that earthquake don’t kill, but that will be done by poorly built constructions. Earthquake resistant buildings can be made, only by constructing our homes with ductile character. For a better understanding in earthquake resistant buildings, we must acquire knowledge about earthquakes and its occurrence. The points are given as below;

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SEISMIC VULNERABILITY ASSESSMENT of SCHOOL BUILDINGS: GAZA STRIP SCHOOLS as a CASE STUDY
BY
S. M. Shehada 1, S. Q. Shurrab 2
1,2 Department of Civil Engineering, Islamic University of Gaza, Gaza Strip, Palestine

Abstract
This study introduces a new approach for seismic assessment of existing school buildings. The proposed approach requires minimum human effort as it can be implemented by a small team of technical construction background. The approach is based on EMS-98 scale in addition to rapid survey of architectural and structural elements of existing school buildings. The study uses 64 selected public school buildings sampled from a total of 364 schools in Gaza Strip. The results showed that 50% of the surveyed schools are classified as Vulnerability class B, while 20 % are classified as Vulnerability Class A. The results were verified using the ‘probability matrix damage’ approach and showed good satisfying convergence. The results of the study are beneficial for the responsible parties who are expected to take appropriate actions related to enhancing seismic performance of Gaza Strip schools against seismic activities, due to the fact that these school buildings not only host about 450,000 students and teachers, but also serve as emergency shelters for those who lose their homes as a result of political instabilities in the region.

Keywords: Damage, Vulnerability, EMS-98, Seismic risk, structural type.

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By
M.RAJAGOPAL REDDY 1, P.RAJESH 2
1- Post Graduate student, Department of civil Engineering,VFSTR university , Vadlamudi.
2-Assistant Professor, Department of civil Engineering, VFSTR university, Vadlamudi.

ABSTRACT
The FLAT SLAB SYSTEM being used in majority of the constructions. It elevates more clear space in architecting the construction design in easy manner and duration of construction would be short due to the flat slabs size. Compare to the traditional concrete construction slab system is more viable due to the fact that it avoids the heavy beams, which are the big vulnerability in case of earthquakes. Objective of this paper is to investigate the behavior of flat slab system in few different use cases.

1. Flat slab structure without drop.
2. Flat slab structure with column drop.
3. Flat slab structure with shear wall.
4. Flat slab structure with column drop and shear wall together through response spectrum method by using ETABS software.

The behavior of flat slab is investigated in terms of the following factors:
1. Frequency
2. Base Shear
3. Storey level accelerations

Also most severe problem in flat slabs as follows:
1. Failure punching shears
2. Shear stresses during ground unbalance
3. Slab column connections to brittle punching shear stresses during earthquakes.

Also this paper investigates about the combinations that can produce less punching shear at slab column joint.

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By
Priyanka Gupta

1.0 Introduction
In April 2016, 81 new towns and cities were added to a list of areas prone to earthquakes, bringing the total to 107. In 2012, BIS has introduced special earthquake resistant steel in India standard 1786 for HYSD bars. But this still needs a mention in design code of IS 456 for design help. There are few manufacturers in India which make earthquake resistant steel with grade name as Fe 500 SD which can be used in seismic resistant designed buildings.

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India has been plagued by some catastrophic earthquake tremors in past that have caused loss of property and human beings:

However, during the earthquake in New Zealand on 3^rd September 2010 (magnitude on Richter’s scale: 7.0), only 2 people were injuredwhich was caused by falling masonry and glass. Interestingly, the said earthquake had struck when most people were asleep. Therefore it is clear that “EARTHQUAKES DON’T KILL PEOPLE, BUILDINGS DO!”
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By
NAVNEET KUMAR,B.Tech(CE)
2^nd year, ITM UNIVERSITY, GWALIOR

Experience in past earthquakes has demonstrated that many common buildings and typical methods of construction lack basic resistance to earthquake forces in most cases this resistance can be achieved by following simple inexpensive principles of good building construction practices . Adherence to these  simple rules will not prevent all damage in moderate or large earthquakes, but life threatening collapses should be prevented, and damage limited to repairable proportions. These principles fall into several broad categories:-
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